Autots

* updated metrics
* Cassandra bug fixes
* fail_on_forecast_nan now also checks for infinity, and is faster

* Cassandra seasonality, holiday detection, and other bug fixes
* attempted to improve the KalmanStateSpace and KalmanSmoothing methods
* validation indexes now generated in a standalone function
* create_regressor bug fix
* added MLEnsemble
* fix a bug where common_fourier failed on short length forecasts
* added some additional options to ARDL
* refactored metric df eval
* refactored parts of AutoTS for templates and validations
* added ewmae metric
* non Horizontal ensembles are now also constructed after validations and vals are rerun

* robustness changes to generate_score_per_series for horizontal ensembles
* added generation_timeout to allow stopping based on time
* added ability to specify anomaly model (ie 'zscore') to AnomalyDetector.get_new_params(method='zscore')
* fixed a bug in Cassandra with future_impacts and future_regressor

* allow transformer_max_depth == 0
* linear_tree option to LightGBM models
* additional linear model options to Cassandra

* add LocalLinearTrend transformer
* improved ScipyFilter focusing on Butter and Savitzky–Golay filters
* update to AutoTS().back_forecast including breaking change of `column` arg renamed to `series`
* add KalmanSmoothing transformer
* add KalmanStateSpace model (Kalman Filter + 'any' state space models)
* AlignLastValue no longer applied to upper/lower forecast bounds
* modified `regression` impact in HolidayTransformer to weighted least squares, moved existing to 'datepart_regression'
* added Cassandra model
* bug fix for Categorical dateparts with 1 starts
* updated load_daily to Wikimedia page views
* added dwae metric
* added MetricMotif model
* added 'common_fourier' datepart method
* added SeasonalMotif model
* added 'seasonal' validation
* bug fix for cffilter with univariate input

* added AnomalyDetector
* added HolidayDetector
* added observation_end and Wikipedia data to load_live_daily
* added binarized versions of datepart method (should have done ages ago!)
* addded RRVAR, MAR, TMF, LATC models
* added AlignLastValue transformer
* added plot_horizontal_model_count and fixed an error in horizontal generation plot
* adjusted TotalRuntime to higher precision, and no longer + 1
* added subsidiary transformer for cleaning in Detrend and Datepart detrend Transformers
* sped up SinTrend transformer
* new AnomalyRemoval transformer
* added HolidayTransformer
* added auto holidays to Prophet
* added get_new_params method to AutoTS class
* more holidays options to create_regressor